His main point is that the "classical liberal" set-up of a minimal state and an open market is the most robust design for a world of actors with limited rationality and limited benevolence.
Along the way, he makes a couple of interesting points. One has to do with the nature of competition between firms. If one or two firms are winning and others are losing, the government can step in to try to impose its concept of perfect competition. But, Professor Pennington says, "it's precisely through these 'imperfections' that learning happens," as firms copy the behavior of the winners and avoid the behavior of the losers. Things become more equal on their own.
Second, he says that markets are held to a different standard than government regulators are held to.